1. Field of the Invention
The present invention relates to an airbag for a vehicle, more particularly to an airbag system for a vehicle which is capable of using a smaller capacity of inflator by preventing gas in a housing from being emitting to the outside in the early stage of spreading an air cushion.
2. Description of the Related Art
Recently, people are getting more and more interested in safety as well as functionality and convenience of a car when driving a car. As a result, the safety devices for protecting passengers also become important at automobile accidents as well.
Among these devices, an airbag system is used, along with a seat belt, to prevent a passenger in the head, breast or knees from being injured against constructions in the car in an automobile accident.
On the other hand, the airbag system is often installed in the front seat. Generally, it is classified into a driver airbag built in the steering wheel and a passenger airbag built on the passenger glove box or in the upper clash pad.
FIG. 1 is a perspective view illustrating the structure of a general passenger airbag. As illustrated in FIG. 1, a conventional airbag includes an inflator 10 for generating gas, an inflator housing 20 for accepting the inflator 10, and a retainer (not illustrated) fixed in the upper surface of the inflator housing 20.
In addition, an air cushion (not illustrated) is fixed in the upper surface of the retainer, and an air cushion housing 30 for accepting the air cushion is coupled to the upper surface of the inflator housing 20.
The inflator 10 is electrically connected to a sensor which senses a car collision, and it generates gas by means of signals from the sensor to be emitted into the air cushion.
The air cushion is accepted in the folded form in the air cushion housing 30 and expanded into a predetermined form by receiving gas from the inflator 10.
On the other hand, the air cushion includes gas discharge holes for emitting gas to the outside to alleviate the shock when in contact with a passenger in the condition wherein the cushion is spread or expanded.
Along with the air cushion, the inflator housing 20 includes a plurality of gas discharge holes 22 for doing the same thing with the gas discharge holes of the air cushion.
In short, when spreading the air cushion, the gas discharge holes 22 emit gas from the inflator housing 20 to the outside.
Accordingly, when the sensor detects collision at automobile collision, the signal for operating the airbag is applied to the inflator 10, and the gas from the inflator 10 is charged into the air cushion on the spur of the moment and prevents a passenger from being bumped against the front structure.
At this time, the gas generating from the inflator 10 is emitted to the outside through the gas discharge holes 22 built in the inflator housing 20 to alleviate the passenger's shock caused by momentarily excessive expansion pressure of the air cushion.
However, as for the conventional airbag structure, when spreading the air cushion in the early step, some of the gas from the inflator 10 is sent to the air cushion and at the same time, emitted to the outside through the gas discharge holes 22, which results in unwanted loss of gas.
Thus, when estimating the capacity of inflator 10, an additional amount of gas equal to that emitted to the outside through the gas discharge holes 22 in the early step of spreading the air cushion is required. That's why it is inevitable to use n inflator whose capacity is larger than that of actual inflator needed to spread the air cushion.